Bill McKibben is a prominent American environmentalist, author, and grassroots activist who is widely recognized for his pioneering work on climate change. He wrote The End of Nature (1989), which is regarded as the first book for a general audience about global warming.

He also co-founded 350.org, the first global grassroots climate campaign, and later launched Third Act, an organization that mobilizes Americans over the age of 60 to advocate for climate and racial justice.